[Solved] One of vm in Hyper-V cannot be connected, but the others vm could.

When I try to connect one of vm in Hyper-V, there is no response or pop-up RDP window.
(The green one can be connected but not black one.)

I go to check the service mgt, i found there exist a vmconnect.exe after I exist all vm RDP.
After checked, it will be created since connect to vm.
So I kill the process and connect to black vm again, it is working now.